The present invention relates generally to a method for the synthesis of a sulfurpentafluoride compound. More particularly, the present invention relates generally to a method for the synthesis of an aryl sulfurpentafluoride compound.
The development of synthetic methodologies for the introduction of sulfurpentafluoride or pentafluorosulfuranyl groups (“SF5”) into organic compounds has been pursued with a considerable degree of interest by several research groups. It is believed that the SF5 group may impart unique properties to these organic compounds that include, inter alia, low surface energy, high chemical resistance, high thermal stability, high electronegativity, hydrophobicity, and high dielectric constant. For instance, the high electronegativity value of the SF5 group, 3.62 on the Pauling scale, and greater electron withdrawing ability may make it an attractive alternative for the trifluoromethyl group (“CF3”) found in many commercial products. Aryl sulfurpentafluoride compounds can be used to introduce one or more sulfurpentafluoride groups into an organic compound.
The prior art provides a variety of methods for the synthesis of sulfur pentafluoride compounds such as aryl sulfurpentafluoride compounds. For example, U.S. Pat. Nos. 3,073,861 and 3,219,690 and the references Sheppard, W. A., “Arylsulfur Trifluoride and Pentafluorides”, J. Am. Chem. Soc., 82 (1960), pp. 4751–52 and Sheppard W. A., “Arylsulfur Pentafluoride”, J. Am. Chem. Soc., 84 (1962), pp. 3064–72 (referred to herein collectively as Sheppard) describe a two-step method for preparing aryl sulfurpentafluoride compounds by reacting aryl disulfides or aryl sulfur trifluorides with AgF2. The reported yields of this two-step method were relatively low, i.e., 5 to 35%. Other references, such as, Lentz et al., “The —SF5, —SeF5, and —TeF5 Groups in Organic Chemistry”, CHEMISTRY OF HYPERVALENT COMPOUNDS, Wiley Co., NY, N.Y. (1999), pp. 295–324; Baba, H. et al., “The Electrochemical Fluorination of Ethanethiol”, Bulletin of the Chemical Society of Japan, Vol. 50 (10) (1977), pp. 2809–2810; Abe, T. et al., “The Electrochemical Fluorination of Dithiols and Cyclic Sulfides”, Bulletin of the Chemical Society of Japan, Vol. 46 (1973), pp. 3845–3848 (referred to herein collectively as “Baba”); and Winter, R., et al., “Functionalization of Pentafluoro-λ-sulfanyl (SF5) Olefins and Acetylenes”, INORGANIC FLUORINE CHEMISTRY: TOWARD THE 21ST CENTURY, Thrasher and Strauss, Washington D.C. (1994), pp. 129–66, describe methods of preparing —SF5 containing organics through direct reactions of organic substrates with F5S• reagents, electrochemical fluorinations of organo-sulfur compounds, and functionalization of pentafluorothio acetylenes and olefins, respectively. Each of the aforementioned methods present various processing difficulties such as lack of selectivity, poor yields, over-fluorination, or painstaking purifications.
More recently, published patent application WO 94/22817 and the reference Sipyagin, A. M. et al., “Preparation of the First Ortho-Substituted Pentafluorosulfanylbenzenes”, J. of Fluorine Chem., Vol. 112 (2001), pp. 287–95, describe methods that improve upon Sheppard's two-step method through the use of alternate, non-aqueous solvents or the presence of copper or other metals within the reaction conditions. However, these improved methods still employ high-cost AgF2 as a reagent.
Published patent application WO 97/05106, U.S. Pat. No. 5,741,935, and the reference Bowden, R. D., et al., “A New Method for the Synthesis of Aromatic Sulfurpentafluorides and Studies of the Stability of the Sulfurpentafluoride Group in Common Synthetic Transformations”, Tetrahedron 56 (2000), pp. 3399–3408 (referred to herein collectively as Bowden) describe a commercial process for the preparation of nitrophenyl sulfurpentafluoride by treating the corresponding nitrophenyl disulfides, thiols, or sulfur trifluoride with dilute F2. It appears, however, that the Bowden process is practically limited to deactivated aromatics.
The reference, Ou, X., et al., “Oxidative Fluorination of S, Se, and Te Compounds, J. of Fluorine Chem., 101 (2000), pp. 279–283 (referred to herein as “Ou”), describes a method to synthesize aryl sulfurpentafluoride compounds involving the oxidative fluorination of aromatic sulfur compounds with XeF2, such as that illustrated in Scheme 1. The oxidative fluorination of the sulfur atom to sulfur (VI) fluorides quickly and easily under mild conditions. While the method of Scheme I may be convenient for small-scale laboratory preparations and studies, the cost and availability of XeF2 make this method impractical for commercial production of —SF5 compounds.
In addition to the Ou method, other methods for the oxidative fluorination of sulfur or sulfur-containing compounds include using gaseous fluoroxy reagents such as fluoroxytrifluoromethane (“FTM” or F3COF) or bis(fluoroxy)difluoromethane (“BDM” or F2C(OF)2). For example, the references, Denney, D. B., et al., “Dialkyl- and Diaryltetrafluoropersulfuranes”, J. of the Am. Chem. Soc., Vol. 95:24, Nov. 28, 1973, pp. 8191–92, Bailey, R. E., et al., “Reactions of Trifluoromethyl Hypofluorite with Sulfur and with Other Substances Containing Divalent Sulfur”, Inorganic Chemistry, Vol, 9, No., 8 (1970), pp. 1930–32, and Hohorst, F. A., et al., “Some Reactions of Bis(fluoroxy)difluoromethane, CF2(OF)2”, Inorganic Chemistry, Vol. 7, No. 3 (1968), pp. 624–26, describe the reaction of FTM with dialkyl and diaryl sulfides to yield dialkyl and diaryl tetrafluorosulfuranes, the reaction of FTM with sulfur at room temperature to give S(II) and S(IV)fluorides, and the reaction of BDM with sulfur to yield sulfur tetrafluoride, respectively. Further, the references, Abe T. et al., “Fluorination of Perfluoroalkylsufenyl Chlorides, Perfluorodialky Disulfides and Perfluorodialkyl Sulfides with Chlorine Monofluoride”, J. of Fluorine Chem., Vol. 3 (1973/74), pp. 187–196 and Viets, D., et al., “1,2-Bis[trifluorosulfur(IV)tetrfluoroethane F3S—CF2—CF2—SF3” A Bifunctional Molecule with Two Fluoroamphoteric Sulfur Centers”, Eur. J. Inorg. Chem., Vol. 7 (1998), pp. 1035–39, describe oxidative fluorinations of sulfenyl halides but are limited to those of perfluoroalkanesulfenyl chlorides. Thus, the use of fluoroxy reagents to generate aryl sulfurpentafluoride compounds has remained unexplored.
Despite the foregoing developments, there remains a need in the art for a safe and cost-effective process to make aryl sulfurpentafluoride compounds at greater yields, higher purities, and in a single reaction vessel. Further, there is a need in the art for a synthesis method that produces a high purity aryl sulfurpentafluoride compound without the necessity of extensive purification processes.
All references cited herein are incorporated herein by reference in their entireties.